Magnetic field switches, such as Hall effect sensors, are a type of magnetic sensor with a digital output that toggles from high to low and from low to high when certain levels of magnetic field intensity are sensed. These switches are often used for proximity sensing. The switches yield magnetic field versus output voltage characteristics that include a certain amount of hysteresis in order to provide noise immunity.
The output behavior of these switches can be unipolar, bipolar or omnipolar. In unipolar switches, the output is dependent upon both the magnitude of the field and the polarity. In omnipolar switches, the output is dependent upon the magnitude of the field and not the polarity. For some applications, omnipolar switch behavior is desired over unipolar in that the output does not depend on the polarity of the magnetic field. This may simplify operation and capture of desired behavior. However, omnipolar switches tend to have increased complexity over unipolar switched and require a polarity comparator in order to provide the omnipolar behavior. This increased complexity requires larger area and power consumption among other drawbacks.